An optical window for a hypersonic vehicle includes a window substrate and an optical coating on the window substrate, with the coating including multiple alternating layers of different materials. The coating may have many layers, for example having five or more alternating bi-layers and may be configured to still perform its optical function with some of the layers removed, such as by ablation of some of the layers through exposure to hypersonic flow. The different materials of the different layers may have different properties, for example with one of the materials being more resistant to ablation and/or chemical reaction than another of the layers. Coatings for anti-reflection additionally include a region of graded optical index between the sequence of bi-layers and the substrate. The hypersonic vehicle may include an optical sensor which operates by receiving light through the optical window.